As a driving force transmission mechanism in which a driven shaft is fixed to a plate, a driven structure is pivotally provided around the driven shaft as well as a motor is fixed to the plate, there are two types of mechanisms. In the driving force transmission mechanism of the first type, a driven shaft and a driven structure are at a first side surface of the plate, while a motor is at the other surface side of the plate. In the driving force transmission mechanism of the second type, a driven shaft, a driven structure and a motor are at a first side surface of the plate. As a specific example of the latter case, the one described in JP-A-5-306740 is known.
In these driving force transmission mechanisms, when a motor shaft of the motor rotates, the driving force is transmitted to the driven structure. The driving force of the driven structure is transmitted to other components. Accordingly, the conventional driving force transmission mechanism is applied to, for example, an image forming apparatus, in which paper can be fed.